Many medical and physical conditions will affect the proper functioning of the breathing organs. The effects may be directly related to the physical condition of the lungs themselves and/or the many correlated functions that provide the breathing movements controlling the inspiration and expiration of the lungs. Several diseases have an effect on breathing movements and breathing patterns such that, e.g., movements of either the upper or lower chest or abdomen are diminished, affecting the proper respiration and ventilation of the subject. After operations on the chest or upper abdominal area, such as heart or lung operations where the chest has to be opened, subjects commonly have post-operative breathing complications.
Methods of measuring breathing movements include measuring the circumference of the chest and abdomen with a common measuring tape during inspiration and expiration (in- and out-breathing), such a measurement will, however, not give a simultaneous measuring during the same breath at more than one location. It is also difficult to obtain reproducible and precise measurements of changes in the circumference.
Respitrace (™) is a device based on ‘respiratory inductive pletysmography’ and provides time-dependent circumference measurements at two different heights simultaneously (see, e.g., Verschakelen, J. A., Demets, M. G. Am. J. Resp. Critical Care Med. 151, 1995, 399-405). Two spirals are put around the subject and changes in the circumference change the length of the spirals and thus their electrical conductivity.
In studies with a magnetometer the change in diameter is measured at two points at the center of the subject, typically on the center of the sternum and on the abdomen (e.g., Sharp, J. T., et al. J. App. Physiol. 39, 1975, 608-618). Two pairs of electrical coils are placed in contact with the body of the subject such that one coil of each is in front of the body and the other is directly behind the body. An AC current is led to the posterior coils which induces an electromagnetic field between the posterior and anterior coils and a potential is measured in the anterior coils that changes as the distance between the coils changes with the breathing of the subject. None of the above methods will allow a detailed and well-resolved analysis of breathing movements, such as e.g. to obtain symmetry-resolved data.
The Elite system (see U.S. Pat. No. 4,706,296) used in a study by De Groote et al. (De Groote et al. J. Appl. Physiol. 83 (5): 1531-1537, 1997) measures chest wall motions by recording the position of markers placed on an object in motion by using television cameras that have different viewpoints. The system supplies the acquisition of two-dimensional frames for each camera and then computes 3D coordinates of each marker as a function of time. The system as described by De Groote et al. uses two television cameras, and the motion of different subsets of markers is determined by comparing image data from six successive acquisitions, where the orientation of the subject is changed relative to the cameras in between every two acquisitions.
No systems have however been suggested in the prior art, wherein breathing patterns are obtained by measuring the simultaneous movement of a plurality of points, wherein the movement is measured by the change in the distance from each point to a reference point, such that a breathing pattern may be obtained in a single acquisition.
In particular, no such methods have been suggested for measuring the symmetry of breathing movements, that is whether the left and right side of a subject show equal breathing movements or whether a particular breathing problem will affect one side of the body more than the other. This can be suspected, e.g., in many heart operations where the sternum is cleaved and the left side of the rib cage may be forced upwards 3.5-5.5 cm during the operation. No data however seems to be available in the medical literature, discussing or describing post-operative effects on breathing movements, after such invasive surgery, and indeed, the inventors are not aware of any data discussing symmetry/asymmetry of breathing and quantitative measurements thereof. Methods will therefore be appreciated, to monitor such post-operative conditions and other conditions which may affect breathing symmetry and other breathing parameters.
An earlier disclosure by the inventor outlines a possible setup for breathing movement measurements based on using distance sensors. (Ragnarsd{dot over (o)}ttir, Icel. Med. J. vol. 85, no. 4,1999, pp. 313-314.)
It has since been found that such an instrumental setup and other types of imaging devices can be. used to determine breathing patterns which can be described by a novel set of breathing pattern parameters.